I would think cell phones fall under the de minimis. A handy resource for that: https://www.irs.gov/publications/p15b/index.html
I would put most issues into two main categories:
1. high dollar benefits (i.e. cars bought by the company and used for personal use - taxed as a fringe benefit and will show up on the W-2), and
2. benefits for the owner (the idea being that you can't start a company and just run through personal expenses for the owner).
Logically, I agree with everything your saying, and thank you for the link I will check that out. I find it interesting that your #2 while making sense to me, contradicts what the "Rich Dad Poor Dad author, Robert Kiyosaki, who is a multi millionaire even before writing his books talks about doing exactly that in a legal way with almost everything.
Right, in a legal way, being the key phrase.
For example, the car is legal as long as you allocate the costs or deduct it on a per-mile basis. 53.5 cents per mile is very generous (especially if you buy a used car for $4,000. It doesn't take long to recover that cost and then come out ahead). If you have a true home office within the IRS definition, you can deduct a pro-rata amount of utilities/insurance/taxes - things you would have to pay with all post-tax money without a business.
You can also find accountants that won't look too closely and will let you deduct a lot of things you probably shouldn't, or that they call a "gray" area. I'm not a fan of these accountants, as they generally give the rest of us a bad reputation when we get a client and tell them they can't deduct expenses. No one likes to have their tax bill increase, even if it was artificially low.
I believe setting up a C-corp also allows deductions that a pass-through entity would not. I was merely speaking to your LLC/S-corp question.
Long story short, there are nuances to almost everything in the tax world. As I often say, taxes are not as black and white as people like to think.